Acoustic reflection of an elastic plate with periodic ribs and a back cavity

摘要

To clarify the acoustic properties of room boundaries, effects of acoustic radiation due to surface vibration should be taken into account. Room boundaries often have a complicated construction, e.g. ribs attached to back surfaces of interior walls, back cavities between interior and exterior wails, etc. The effect of such construction should be considered in order to predict the sound field in a room. This paper describes the theory to analyse the reflected sound held from an infinite elastic plate with periodic ribs and a back cavity. An exact solution is presented in closed form. Some numerical examples of the oblique-incident reflection coefficient are presented. The effects of the parameters of the sound reflection system are discussed. The reflectivity of an infinite elastic plate with periodic ribs and a back cavity significantly dips at low frequencies. This dip is caused by the plate-cavity mass-spring resonance. Also, higher mode plate vibrations due to the ribs cause many sharp dips in the reflection coefficient. The rib effect also causes the reflectivity of the plate to increase to a certain extent at low frequencies. Some examples of field-incidence-averaged absorption coefficient of panel absorbers, calculated by the present theory, are presented and found in fairly good agreement with measured results. [References: 34]